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</code></pre></div><ul><li>toJS()：将一个Immutable数据转换为JS类型的数据</li> <li>is()：对两个对象进行比较</li></ul> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">import</span> <span class="token punctuation">{</span> Map<span class="token punctuation">,</span> is <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'immutable'</span>
<span class="token keyword">const</span> map1 <span class="token operator">=</span> <span class="token function">Map</span><span class="token punctuation">(</span><span class="token punctuation">{</span> a<span class="token operator">:</span> <span class="token number">1</span><span class="token punctuation">,</span> b<span class="token operator">:</span> <span class="token number">1</span><span class="token punctuation">,</span> c<span class="token operator">:</span> <span class="token number">1</span> <span class="token punctuation">}</span><span class="token punctuation">)</span>
<span class="token keyword">const</span> map2 <span class="token operator">=</span> <span class="token function">Map</span><span class="token punctuation">(</span><span class="token punctuation">{</span> a<span class="token operator">:</span> <span class="token number">1</span><span class="token punctuation">,</span> b<span class="token operator">:</span> <span class="token number">1</span><span class="token punctuation">,</span> c<span class="token operator">:</span> <span class="token number">1</span> <span class="token punctuation">}</span><span class="token punctuation">)</span>
map1 <span class="token operator">===</span> map2   <span class="token comment">//false</span>
Object<span class="token punctuation">.</span><span class="token function">is</span><span class="token punctuation">(</span>map1<span class="token punctuation">,</span> map2<span class="token punctuation">)</span> <span class="token comment">// false</span>
<span class="token function">is</span><span class="token punctuation">(</span>map1<span class="token punctuation">,</span> map2<span class="token punctuation">)</span> <span class="token comment">// true</span>
</code></pre></div><ul><li><p>get(key)：对数据或对象取值</p></li> <li><p>getIn([]) ：对嵌套对象或数组取值，传参为数组，表示位置</p></li></ul> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> abs <span class="token operator">=</span> Immutable<span class="token punctuation">.</span><span class="token function">fromJS</span><span class="token punctuation">(</span><span class="token punctuation">{</span>a<span class="token operator">:</span> <span class="token punctuation">{</span>b<span class="token operator">:</span><span class="token number">2</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
abs<span class="token punctuation">.</span><span class="token function">getIn</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">'a'</span><span class="token punctuation">,</span> <span class="token string">'b'</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token comment">// 2</span>
abs<span class="token punctuation">.</span><span class="token function">getIn</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">'a'</span><span class="token punctuation">,</span> <span class="token string">'c'</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token comment">// 子级没有值</span>

<span class="token keyword">let</span> arr <span class="token operator">=</span> Immutable<span class="token punctuation">.</span><span class="token function">fromJS</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">1</span> <span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token punctuation">{</span>a<span class="token operator">:</span> <span class="token number">5</span><span class="token punctuation">}</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
arr<span class="token punctuation">.</span><span class="token function">getIn</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token string">'a'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 5</span>
arr<span class="token punctuation">.</span><span class="token function">getIn</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token string">'c'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 子级没有值</span>
</code></pre></div><ul><li></li></ul> <p>如下例子：使用方法如下：</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">import</span> Immutable <span class="token keyword">from</span> <span class="token string">'immutable'</span><span class="token punctuation">;</span>
foo <span class="token operator">=</span> Immutable<span class="token punctuation">.</span><span class="token function">fromJS</span><span class="token punctuation">(</span><span class="token punctuation">{</span>a<span class="token operator">:</span> <span class="token punctuation">{</span>b<span class="token operator">:</span> <span class="token number">1</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
bar <span class="token operator">=</span> foo<span class="token punctuation">.</span><span class="token function">setIn</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">'a'</span><span class="token punctuation">,</span> <span class="token string">'b'</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>   <span class="token comment">// 使用 setIn 赋值</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>foo<span class="token punctuation">.</span><span class="token function">getIn</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">'a'</span><span class="token punctuation">,</span> <span class="token string">'b'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>  <span class="token comment">// 使用 getIn 取值，打印 1</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>foo <span class="token operator">===</span> bar<span class="token punctuation">)</span><span class="token punctuation">;</span>  <span class="token comment">//  打印 false</span>
</code></pre></div><p>如果换到原生的<code>js</code>，则对应如下：</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> foo <span class="token operator">=</span> <span class="token punctuation">{</span>a<span class="token operator">:</span> <span class="token punctuation">{</span>b<span class="token operator">:</span> <span class="token number">1</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> bar <span class="token operator">=</span> foo<span class="token punctuation">;</span>
bar<span class="token punctuation">.</span>a<span class="token punctuation">.</span>b <span class="token operator">=</span> <span class="token number">2</span><span class="token punctuation">;</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>foo<span class="token punctuation">.</span>a<span class="token punctuation">.</span>b<span class="token punctuation">)</span><span class="token punctuation">;</span>  <span class="token comment">// 打印 2</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>foo <span class="token operator">===</span> bar<span class="token punctuation">)</span><span class="token punctuation">;</span>  <span class="token comment">//  打印 true</span>
</code></pre></div><h2 id="三、在react中应用"><a href="#三、在react中应用" class="header-anchor">#</a> 三、在React中应用</h2> <p>使用 <code>Immutable</code>可以给 <code>React</code> 应用带来性能的优化，主要体现在减少渲染的次数</p> <p>在做<code>react</code>性能优化的时候，为了避免重复渲染，我们会在<code>shouldComponentUpdate()</code>中做对比，当返回<code>true</code>执行<code>render</code>方法</p> <p><code>Immutable</code>通过<code>is</code>方法则可以完成对比，而无需像一样通过深度比较的方式比较</p> <p>在使用<code>redux</code>过程中也可以结合<code>Immutable</code>，不使用<code>Immutable</code>前修改一个数据需要做一个深拷贝</p> <div class="language-jsx extra-class"><pre class="language-jsx"><code><span class="token keyword">import</span> <span class="token string">'_'</span> <span class="token keyword">from</span> <span class="token string">'lodash'</span><span class="token punctuation">;</span>

<span class="token keyword">const</span> Component <span class="token operator">=</span> React<span class="token punctuation">.</span><span class="token function">createClass</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
  <span class="token function">getInitialState</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">return</span> <span class="token punctuation">{</span>
      data<span class="token operator">:</span> <span class="token punctuation">{</span> times<span class="token operator">:</span> <span class="token number">0</span> <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>
  <span class="token punctuation">}</span><span class="token punctuation">,</span>
  <span class="token function">handleAdd</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">let</span> data <span class="token operator">=</span> _<span class="token punctuation">.</span><span class="token function">cloneDeep</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>state<span class="token punctuation">.</span>data<span class="token punctuation">)</span><span class="token punctuation">;</span>
    data<span class="token punctuation">.</span>times <span class="token operator">=</span> data<span class="token punctuation">.</span>times <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">;</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">setState</span><span class="token punctuation">(</span><span class="token punctuation">{</span> data<span class="token operator">:</span> data <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><p>使用 Immutable 后：</p> <div class="language-jsx extra-class"><pre class="language-jsx"><code><span class="token function">getInitialState</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  <span class="token keyword">return</span> <span class="token punctuation">{</span>
    data<span class="token operator">:</span> <span class="token function">Map</span><span class="token punctuation">(</span><span class="token punctuation">{</span> times<span class="token operator">:</span> <span class="token number">0</span> <span class="token punctuation">}</span><span class="token punctuation">)</span>
  <span class="token punctuation">}</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
  <span class="token function">handleAdd</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">setState</span><span class="token punctuation">(</span><span class="token punctuation">{</span> data<span class="token operator">:</span> <span class="token keyword">this</span><span class="token punctuation">.</span>state<span class="token punctuation">.</span>data<span class="token punctuation">.</span><span class="token function">update</span><span class="token punctuation">(</span><span class="token string">'times'</span><span class="token punctuation">,</span> <span class="token parameter">v</span> <span class="token operator">=&gt;</span> v <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token comment">// 这时的 times 并不会改变</span>
    console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>state<span class="token punctuation">.</span>data<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">'times'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
</code></pre></div><p>同理，在<code>redux</code>中也可以将数据进行<code>fromJS</code>处理</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">import</span> <span class="token operator">*</span> <span class="token keyword">as</span> constants <span class="token keyword">from</span> <span class="token string">'./constants'</span>
<span class="token keyword">import</span> <span class="token punctuation">{</span>fromJS<span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'immutable'</span>
<span class="token keyword">const</span> defaultState <span class="token operator">=</span> <span class="token function">fromJS</span><span class="token punctuation">(</span><span class="token punctuation">{</span> <span class="token comment">//将数据转化成immutable数据</span>
    home<span class="token operator">:</span><span class="token boolean">true</span><span class="token punctuation">,</span>
    focused<span class="token operator">:</span><span class="token boolean">false</span><span class="token punctuation">,</span>
    mouseIn<span class="token operator">:</span><span class="token boolean">false</span><span class="token punctuation">,</span>
    list<span class="token operator">:</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
    page<span class="token operator">:</span><span class="token number">1</span><span class="token punctuation">,</span>
    totalPage<span class="token operator">:</span><span class="token number">1</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span>
<span class="token keyword">export</span> <span class="token keyword">default</span><span class="token punctuation">(</span><span class="token parameter">state<span class="token operator">=</span>defaultState<span class="token punctuation">,</span>action</span><span class="token punctuation">)</span><span class="token operator">=&gt;</span><span class="token punctuation">{</span>
    <span class="token keyword">switch</span><span class="token punctuation">(</span>action<span class="token punctuation">.</span>type<span class="token punctuation">)</span><span class="token punctuation">{</span>
        <span class="token keyword">case</span> constants<span class="token punctuation">.</span><span class="token constant">SEARCH_FOCUS</span><span class="token operator">:</span>
            <span class="token keyword">return</span> state<span class="token punctuation">.</span><span class="token function">set</span><span class="token punctuation">(</span><span class="token string">'focused'</span><span class="token punctuation">,</span><span class="token boolean">true</span><span class="token punctuation">)</span> <span class="token comment">//更改immutable数据</span>
        <span class="token keyword">case</span> constants<span class="token punctuation">.</span><span class="token constant">CHANGE_HOME_ACTIVE</span><span class="token operator">:</span>
            <span class="token keyword">return</span> state<span class="token punctuation">.</span><span class="token function">set</span><span class="token punctuation">(</span><span class="token string">'home'</span><span class="token punctuation">,</span>action<span class="token punctuation">.</span>value<span class="token punctuation">)</span>
        <span class="token keyword">case</span> constants<span class="token punctuation">.</span><span class="token constant">SEARCH_BLUR</span><span class="token operator">:</span>
            <span class="token keyword">return</span> state<span class="token punctuation">.</span><span class="token function">set</span><span class="token punctuation">(</span><span class="token string">'focused'</span><span class="token punctuation">,</span><span class="token boolean">false</span><span class="token punctuation">)</span>
        <span class="token keyword">case</span> constants<span class="token punctuation">.</span><span class="token constant">CHANGE_LIST</span><span class="token operator">:</span>
            <span class="token comment">// return state.set('list',action.data).set('totalPage',action.totalPage)</span>
            <span class="token comment">//merge效率更高，执行一次改变多个数据</span>
            <span class="token keyword">return</span> state<span class="token punctuation">.</span><span class="token function">merge</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
                list<span class="token operator">:</span>action<span class="token punctuation">.</span>data<span class="token punctuation">,</span>
                totalPage<span class="token operator">:</span>action<span class="token punctuation">.</span>totalPage
            <span class="token punctuation">}</span><span class="token punctuation">)</span>
        <span class="token keyword">case</span> constants<span class="token punctuation">.</span><span class="token constant">MOUSE_ENTER</span><span class="token operator">:</span>
            <span class="token keyword">return</span> state<span class="token punctuation">.</span><span class="token function">set</span><span class="token punctuation">(</span><span class="token string">'mouseIn'</span><span class="token punctuation">,</span><span class="token boolean">true</span><span class="token punctuation">)</span>
        <span class="token keyword">case</span> constants<span class="token punctuation">.</span><span class="token constant">MOUSE_LEAVE</span><span class="token operator">:</span>
            <span class="token keyword">return</span> state<span class="token punctuation">.</span><span class="token function">set</span><span class="token punctuation">(</span><span class="token string">'mouseIn'</span><span class="token punctuation">,</span><span class="token boolean">false</span><span class="token punctuation">)</span>
        <span class="token keyword">case</span> constants<span class="token punctuation">.</span><span class="token constant">CHANGE_PAGE</span><span class="token operator">:</span>
            <span class="token keyword">return</span> state<span class="token punctuation">.</span><span class="token function">set</span><span class="token punctuation">(</span><span class="token string">'page'</span><span class="token punctuation">,</span>action<span class="token punctuation">.</span>page<span class="token punctuation">)</span>
        <span class="token keyword">default</span><span class="token operator">:</span>
            <span class="token keyword">return</span> state
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><h2 id="参考文献"><a href="#参考文献" class="header-anchor">#</a> 参考文献</h2> <ul><li>https://zhuanlan.zhihu.com/p/20295971?spm=a2c4e.11153940.blogcont69516.18.4f275a00EzBHjr&amp;columnSlug=purerender</li> <li>https://www.jianshu.com/p/7bf04638e82a</li></ul></div> <footer class="page-edit"><!----> <div class="last-updated"><span class="prefix">更新时间:</span> <span class="time">12/14/2021, 10:12:35 AM</span></div></footer> <div class="page-nav"><p class="inner"><span class="prev">
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